Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $105.60   8.869%   $114.9657   $114.97   $114.95   $115.00  
  Purchase #2 $190.39   6.281%   $202.3484   $202.35   $202.35   $202.30  
  Purchase #3 $218.30   7.191%   $233.998   $234.00   $234.00   $234.00  
  Purchase #4 $53.44   8.753%   $58.1176   $58.12   $58.10   $58.10  
  Purchase #5 $107.59   4.537%   $112.4714   $112.47   $112.45   $112.50  
  Purchase #6 $147.40   4.473%   $153.9932   $153.99   $154.00   $154.00  
  Purchase #7 $45.93   6.704%   $49.0091   $49.01   $49.00   $49.00  
  7 purchase totals = $868.65       $924.9034   $924.91   $924.85   $924.90